Panic on pool.SetSize(5) via http request

[4n70w4]

var pool tunny.Pool

...

	numCPUs := runtime.NumCPU()

	pool := tunny.NewFunc(numCPUs, func(payload interface{}) interface{} {
		time.Sleep(time.Second)
		log.Println(fmt.Sprintf("superprocess %v", payload))

		return nil
	})
	pool.SetSize(1)
	defer pool.Close()

...

	http.HandleFunc("/tune", endpointTune)

...


	go func() {

		for {
			for Deque.Len() != 0 {
				go pool.Process(Deque.PopFront())
			}
			time.Sleep(time.Second)
		}
	}()

package main

import (
	"net/http"
)


type TuneRequest struct {
	PoolSize int
}


func endpointTune(res http.ResponseWriter, req *http.Request) {
	r := TuneRequest{}

	err := decoder.Decode(&r, req.URL.Query())

	if err != nil {
		return
	}

	pool.SetSize(r.PoolSize)
}

2020/04/07 11:45:23 http: panic serving [::1]:57105: runtime error: invalid memory address or nil pointer dereference
goroutine 27 [running]:
net/http.(*conn).serve.func1(0xc0000a2b40)
	/Go/src/net/http/server.go:1772 +0x150
panic(0x840e40, 0xb3e540)
	/Go/src/runtime/panic.go:973 +0x429
github.com/Jeffail/tunny.(*Pool).SetSize(0xb4b460, 0x5)
	/Go/bin/src/github.com/Jeffail/tunny/tunny.go:236 +0x108
main.endpointTune(0x90ef20, 0xc00010c000, 0xc000132100)
	/src/endpointTune.go:24 +0xf4
net/http.HandlerFunc.ServeHTTP(0x8bc580, 0x90ef20, 0xc00010c000, 0xc000132100)
	/Go/src/net/http/server.go:2012 +0x4b
net/http.(*ServeMux).ServeHTTP(0xb4b4e0, 0x90ef20, 0xc00010c000, 0xc000132100)
	/Go/src/net/http/server.go:2387 +0x1ad
net/http.serverHandler.ServeHTTP(0xc000180000, 0x90ef20, 0xc00010c000, 0xc000132100)
	/Go/src/net/http/server.go:2807 +0x216
net/http.(*conn).serve(0xc0000a2b40, 0x90f520, 0xc0000e1780)
	/Go/src/net/http/server.go:1895 +0x171d
created by net/http.(*Server).Serve
	/Go/src/net/http/server.go:2933 +0x938

[fairyhunter13]

@4n70w4 You use pool := ..... It should be pool = .....

[4n70w4]

@fairyhunter13 but what does it have to do with it?

[doron-cohen]

When you use pool := tunny... you redefine pool inside the function scope. The global var pool tunny.Pool stays uninitialized. So, when you refer to it in endpointTune it's value is nil and you basically get nil pointer dereference.